The present invention relates to a centrifugal compressor, and, more particularly, to a centrifugal compressor for use in turbo-refrigerators which enables significant reduction in the manufacturing cost.
There has been an increased demand for higher performance, more compactness and cost reduction in turbo refrigerator construction. Accordingly, when centrifugal compressor is used with a turbo-refrigerator, etc., there has also been an increased demand for further compactness and cost reduction.
Attempts have been made to meet the above demands by providing a drive motor of the smallest size possible appropriate for the centrifugal compressor specified. Nevertheless, it is still necessary for further cost reduction to provide a structure of the type which allows for a reduction in the number of parts or simplification of the manufacturing process.
In a conventional centrifugual compressor for use in turbo-chargers such as, for example, proposed in Japanese Laid Open Application No. 64189/80, the drive system casing is divided into a motor casing section for accommodating a drive motor, and a gear casing section for accommodating a multiplying gear, with the gear casing section and the motor casing section being axially separated or spaced from one another. Furthermore, the gear casing section is connected to the motor casing section by, for example, fastening bolts applied through bolt holes in a flange welded to an abutting end of the motor casing section, with O-rings inserted between the flange and the gear casing section for effecting a hermetic sealing.
Accordingly, with a conventional centrifugal compressor of the aforementioned type, the provision of, for example, fastening bolts, O-rings, etc., necessary for connection of the two casing sections, results not only in an increase in the number of parts but also in an increase in the manufacturing costs by virtue of the need to increase the manufacturing processes for, for example, machining bolt holes in the flange or machining contact surfaces of the flange. Moreover, it is difficult to ensure an accurate fitting of the mutiplying gear mechanism relative to the drive motor.
Therefore, an object of the invention is to provide a centrifugal compressor for use in, for example, a turbo-refrigerator a reduction in which enables reducing the manufacturing cost through a reduction in the working processes involved in the machining and assembly of the centrifugal compressor.
According to the invention, a centrifugal compressor is provided comprising a multiplying gear mechanism including a first shaft having a multiplying gear and directly connected with the rotor of a drive motor, with a second shaft mounting an impeller and having a pinion meshing with the multiplying gear. Bearings respectively support the first and second shafts, with the first and second shafts and bearings being accomodated within a casing. The first shaft includes a rotor shaft of the drive motor and a gear shaft carrying the multiplying gear and detachably connected directly with the rotor shaft of the drive motor. The casing includes a motor casing frame section, a gear casing frame section and bearing casing frame sections respectively accomodating the drive motor, multiplying mechanism and bearings and is integrally formed as a unitary body.